The present invention relates generally to electrophotography, more particularly, to an improved design for the housing of a printer or copier that uses replaceable cartridges comprising an integral shutter apparatus for preventing ambient light from contacting the photoreceptor.
Electrophotographic imaging process (or xerography) is a well-known method of copying or otherwise printing documents. In general, electrophotographic imaging uses a charge-retentive, photosensitive surface (known as a photoreceptor) that is initially charged uniformly. The photoreceptor is most typically in the form of a photosensitive drum or a photosensitive belt. The surface of the photoreceptor is then exposed to a light image representation of a desired image that discharges specific areas of the photoreceptor surface creating a latent image. Toner powder is applied by using a developing system, which carries the toner from a toner container to the photoreceptor surface at selected portions defining the latent image, thereby forming a developed image. This developed image is then transferred from the photoreceptor to a substrate (e.g. paper, transparency, and the like) and the printed copy is produced in a finishing step that fixes the toner to the substrate resulting in the final image. The final image quality is a reflection of the precision and reproducibility of the physical parameters required to create an image on the photoreceptor, the transfer of toner to the image formed on the photoreceptor, and the subsequent transfer of toner from the image-defined areas of the photoreceptor to a substrate. Therefore, the integrity of the photoreceptor surface is a critical feature for all electrophotographic apparatus.
A color or xe2x80x9ctone-on-tonexe2x80x9d electrophotographic imaging process is typically achieved by repeating the same process described above for each color or tone of toner desired thereby serially applying latent color images to the photoreceptor until all desired colors or tones are achieved and then transferring the color image to a substrate. Due to the requirement to sequentially apply latent images for each individual color, the tolerances for the toner transfer processes in a color apparatus are significantly more exacting than in a black and white printing apparatus, and the requirements for image quality are substantially more demanding. Therefore, for color printing apparatus, the integrity of the photoreceptor is an even more critical parameter in producing a high quality image.
For both color and monochrome printing apparatus, the toner is supplied in a replaceable developer cartridge that is purchased separately by the user and may be easily replaced when the toner is completely used. To replace a developer cartridge, the user manually removes the old cartridge from the printer/copier and then inserts a new cartridge. Because the developer cartridge contains the toner that must be transferred to the photoreceptor, and therefore must be stored in very close physical proximity to the photoreceptor, the process of replacing a developer cartridge necessarily exposes the photoreceptor to the external atmosphere during the period of time in which the used developer cartridge is removed and prior to the point at which the new developer cartridge is inserted. In current systems, ambient light may enter the interior of the housing of the apparatus, and specifically enter into the chamber that contains the cartridge, and contact the photoreceptor when a cartridge is not present in the cartridge chamber. Similarly, if a depleted toner cartridge is removed and not immediately replaced with a new cartridge, the photoreceptor will be continually exposed to ambient light during the entire period of time in which a developer cartridge is not in place. When exposed to ambient light, the photoreceptor becomes deteriorated, and with repeated or prolonged exposure to ambient light, the integrity of the photoreceptor will be comprised. Under such conditions, the capability of the photoreceptor to receive toner to create the latent image, and the subsequent transfer to substrate, will be less precise and the quality of the image will be reduced. Therefore, a need exists for an improved design for an electrophotographic apparatus that avoids deterioration of the photoreceptor from exposure to ambient light and that preserves the quality of the images produced by the photoreceptor.
The present invention provides a shutter or cover for the cartridge chamber that acts as an effective closure of the portion of the housing of the apparatus through which replacement developer cartridges are introduced to prevent ambient light from contacting the photoreceptor. The shutter is oriented to completely block ambient light from entering the interior of the housing of the apparatus and may be spring loaded to automatically move into place when a developer cartridge is removed. When a developer cartridge is in place, the shutter rotates into an orientation that does not impede the function or placement of the developer cartridge, but the shutter remains in position for blocking ambient light when the developer cartridge is removed. Preferably, the shutter rotates around a tensioned hinge that biases the shutter into a closed position to substantially block all ambient light from entering the housing of the apparatus.
Other aspects and features of the present invention will become apparent from consideration of the following description taken in conjunction with the accompanying drawings.